Radiologically atypical lymphangioleiomyomatosis presenting with chylous pulmonary congestion, recurrent chylothorax and extrapulmonary cystic lymphatic lesions: A case report.

Lymphangioleiomyomatosis (LAM) is typically recognized by diffuse, bilateral, thin-walled pulmonary cysts on high-resolution computed tomography. However, atypical presentations dominated by lymphatic manifestations and chylous pulmonary congestion may delay diagnosis. We report a 44-year-old woman with progressive exertional dyspnea and recurrent nontraumatic chylothorax. A contrast-enhanced chest and abdominopelvic CT in 2018 had shown multiple extrapulmonary cystic lymphatic lesions involving the mediastinal, retroperitoneal, and bilateral iliac vascular regions, while no obvious pulmonary abnormality was reported. In 2021, imaging showed bilateral pleural effusions, ascites, posterior-predominant patchy pulmonary opacities suggestive of chylous or lymphatic pulmonary congestion, and persistent extrapulmonary cystic lymphatic lesions. Classic diffuse thin-walled pulmonary cysts were not the dominant initial imaging feature. Her history of uterine perivascular epithelioid cell tumor of uncertain malignant potential further complicated the differential diagnosis. Transbronchial cryobiopsy showed enlarged airspaces with spindle-cell proliferation along the walls of enlarged airspaces and focal perivascular distribution. Immunohistochemistry demonstrated positivity for HMB45, smooth muscle actin, and desmin. Serum vascular endothelial growth factor-D was markedly elevated at 5337 pg/mL, supporting sporadic LAM with lymphatic involvement. After sirolimus treatment, the patient remained clinically stable, and imaging showed partial resolution of pulmonary opacities and pleural abnormalities, together with marked reduction of pelvic extrapulmonary cystic lymphatic lesions. Long-term follow-up CT showed several subtle posterior air-containing structures or pulmonary cystic airspace-like changes, some of which could represent small airways or terminal bronchioles rather than definite LAM-related cystic airspaces. The imaging pattern did not evolve into classic diffuse cystic LAM. This case expands the recognized radiological spectrum of LAM and highlights that LAM should be considered when chylous pulmonary congestion and extrapulmonary cystic lymphatic lesions predominate despite nonclassic pulmonary cystic findings.